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Electrically Tunable Phase Shifters With Air-Dielectric Sandwich Structure Minki Jeong, Victor Kazmirenko*, Yuriy Poplavko*, Beomjin Kim, and Sunggi Baik Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 790-784, South Korea * Department of Microelectronics, National Technical University of Ukraine, Kiev, 03056, Ukraine ABSTRACT Electrically tunable microwave phase shifter was developed by inserting dielectric slab and piezoelectric actuator inside a waveguide. Air-dielectric sandwich structure of dielectric material and thin air gap was placed inside a waveguide, where the thickness of air gap is controlled by the actuator. Small changes in the ratio between the thickness of dielectric material and air gap induce significant changes in the effective dielectric constant of the air-dielectric sandwich structure. Phase shifts of 20~200 degrees were realized with the dielectric materials such as (Mg, Ca)TiO3 while the thickness of air gap is changed between 0 to 30 -4

㎛ by piezoelectric control.

Since the dielectric ceramics has very small loss (tanδ ~ 10 ) and the air gap has practically no loss, the total structure shows low insertion loss. INTRODUCTION Microwave phase shifter is one of the essential components for modern microwave communication systems. One interesting application of the phase shifter is devoted to the phased array antenna, where the phase shifters located in one or two dimensional array with differential phase change provide fast steering of microwave signals. Commercial applications include global positioning system (GPS), car collision avoidance radar, aircraft surveillance radar and so on [1]. Development of electrically tunable phase shifters with low loss and low cost have been the key issue for determining the performance and cost of those microwave systems. Electrically tunable phase shifters using either ferrite or PIN diode have supported these microwave systems so far despite of severe disadvantages such as high cost and high insertion loss [2]. Moreover, they have fundamental frequency limitation of increasing loss in the millimeter-wave range where future communication systems may take place. Recently, ferroelectric phase shifters [3], micro-electro-mechanical systems (MEMS) phase shifters [4], and microstrip line phase shifters with piezoelectric control [5] have been studied, yet they are still far from practical applications. We have developed a simple idea of realizing low loss phase shifter by combining well H3.12.1 Downloaded from https://www.cambridge.org/core. Gothenburg University Library, on 08 Feb 2020 at 11:18:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-720-H3.12

known conventional microwave dielectric ceramics and piezoelectric actuator [6]. As a high dielectric constant material is introduced inside a waveguide leaving a small air gap facing upper wall of the waveguide, the effective dielectric constant of the sandwich structure of die